A calendar is a system for organizing and identifying periods of time, typically days, and the names of such identified periods of time are known as calendar dates. Cycles in a calendar are often synchronized with the perceived motion of astronomical objects. A calendar can be a physical device (often paper) that illustrates the system, such as, for example, a desktop calendar or a computer program.
The primary practical uses of a calendar are to identify days, to be informed about and/or to agree on a future event, and to record an event that has happened. Days can be significant for civil, religious or social reasons. For example, a calendar provides a way to determine days that are religious or civil holidays, days that mark the beginning and end of business accounting periods, and days that have legal significance, such as, for example, the day taxes are due or a contract expires. Also a calendar can, by identifying a day, provide other useful information about the day, such as its season.
The calendar in widespread use today is the Gregorian calendar, which is the de facto international standard, and is used almost everywhere in the world for civil purposes, including China and India. The Gregorian calendar is based on a cycle of 400 years, which comprises 146097 days. Since 146097 is evenly divisible by 7, the Gregorian calendar exactly repeats after 400 years. Dividing 146097 by 400 yields an average length of 365.2425 days per calendar year, this is a close approximation to the length of the tropical year. The Gregorian calendar has no inherent dependence on the seven-day week, but in Western society the two are used together, and calendar tools indicate both the Gregorian date and the day of week.
Advantageously, the Gregorian calendar is good for a span of several thousand years, consisting of fourteen one-year calendars, plus a table to show the one-year calendar that is to be used for a given year.
Disadvantageously, however, the Gregorian calendar fails to indicate the dates of moveable holidays such as Christmas and Easter. Further disadvantageously, the current implementations of the Gregorian calendar make it difficult to remember the number of days in a given month, the first day of the month, the last day of the month and the day of the week. Calendar users sometimes remember the number of days in each month of the Gregorian calendar by the use of the traditional mnemonic verse: “Thirty days has (or hath) September, April, June, and November. All the rest have thirty-one, except for February, which has twenty-eight.” A leap year comes once every four years and adds one more day to February. Alternate endings include: “excepting February alone, which has but twenty-eight, in fine, till leap year gives it twenty-nine;” “which has eight and a score, until leap year gives it one day more;” “which has (or hath) twenty-eight days clear, and twenty-nine in each leap year;” and “when short February's done, all the rest have thirty-one.” A language-independent alternative is to hold up two fists with the index knuckle of the left hand against the index knuckle of the right hand. Then, starting with January from the little knuckle of your left hand, count knuckle, space, knuckle through the months. A knuckle represents a month of 31 days, and a space represents a short month of either 30 days or February with 28 or 29 days depending upon leap year. Further disadvantageously, the Gregorian calendar is not perpetual as each year starts on a different day of the week, calendars expire every year, the months are not equal in length, and it is difficult to determine the weekday of any given day of the year.
Although there are many versions of the traditional Gregorian calendar in various forms, such as, for example, day planners, personal organizers, desk calendars and monthly wall calendars, many people, including people with learning disabilities, are unable to use these versions successfully. Advantageously, listed at the top of the traditional calendar are the days of the week from left to right beginning with Sunday and ending on Saturday. The days of the month appear consecutively on each square to represent the day of the week. A month that begins on a Sunday, Monday, Tuesday, Wednesday or Thursday will have five week rows. A month that begins on either a Friday or Saturday will have six week rows.
Disadvantageously, many users have trouble remembering what day of the week the month starts and what day of the week the month ends. Further disadvantageously, it is difficult to visualize the current month on a traditional calendar without looking at either a paper or computer version of the calendar. Additionally, users often have difficulty remembering what months have 30 days and what months have 31 days without resorting to rhyming or knuckle counting.
Currently, paper-and-binder personal organizers are increasingly being supplanted by electronic personal digital assistants (PDAs), cellular telephones and personal information management software such as, for example, Palm® by PalmOne, Franklin Planner® by FranklinCovey, OD4Contact® by Objective Decision, Microsoft® Outlook® by Microsoft Corporation and Time Matters® by LexisNexis®. A traditional calendar, either in paper or computer form, displays rows of boxes to represent the weeks in the month in a four week, five week or six week linear calendar.
Advantageously, computerized calendars offer advanced functionality including the display of multiple calendar months, weekly calendars, daily calendars and hourly calendars for scheduling events.
Disadvantageously, computerized versions of the traditional calendar have limited usefulness because the calendar is only accessible when the computing device is active. Further disadvantageously, the traditional calendar is too large to display effectively on mobile devices such as a cellular telephone.
Although there are many versions of the traditional calendar in various forms, such as, for example, day planners and monthly wall calendars, many people are unable to use these variations successfully. Additionally, many people are also unable to remember calendar events due to the complex calculations and variations between calendars.
Therefore, there exists a need for a calendar that is easy to learn and is more efficient for remembering calendar events in both commercial and non-commercial applications and that is not associated with the disadvantages of the prior art.